I was asked if images should be used in email marketing the other day, here is the advice that I gave the client.

You may want to have a couple of images the first being your logo as it helps your customers identify that it is coming from you, so they feel it is safe to continue reading or click on any of the links within the email.

You may also want to have an image or two in the body content but keep the images small and relavent because Spam filters like to block emails images as they think you are trying to avoid words in the body content by putting them in the images. A good general rule that is a good rule for most things in business is the 80/20 rule for text to images.